This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. PapC is an usher located in the outer membrane of Gram-negative bacteria, responsible for the assembly and secretion of pathogenic P pilus. It is also a platform for the so-called `donor-strand exchange` taking place. Crystal strucutre of PapC will provide important information for understanding how usher recongizing the pilus subunit/chaperone complex, how to translocate pilus subunits, and how to assemle the pilus --- the basic mechanism of so called chaperone-usher pilus biogenesis pathway. We have crystallized PapC, and the crystals diffracted to ~3.2 angstrom at home x-ray machine. the crystals belong to I422, with cell dimentions: a=b=120, c=350. we need beamtime to collected MAD or SAD datasets to determine the first usher structure.